tests: Add formatter test

tests/formatting/in1.blp

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+using Gtk 4.0;using Adw 1;Overlay{Label label{label:_("'Hello World!' \"\n\t\"");}[overlay]Button{notify::icon-name=>$on_icon_name_changed(label)swapped;styles["destructive"]}visible:bind $isVisible(label.visible,my-menu)as<bool>;width-request:bind label.width-request no-sync-create;}menu my-menu{item(_("Label"), "action-name", "icon-name")item{action:"win.format";}}

tests/formatting/in2.blp

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+using Gtk 4.0;
+
+    using Adw 1;
+
+Overlay {
+
+Label
+label
+{
+label
+:
+_
+(
+"'Hello World!' \"\n\t\""
+)
+;
+}
+[
+    overlay
+] Button
+{ notify
+:: icon-name
+=> $ on_icon_name_changed ( label )
+swapped ;
+styles
+[ "destructive" ]
+}
+visible
+: bind $ isVisible ( label.visible ,
+my-menu ) as
+ < bool > ; width-request : bind label . width-request no-sync-create ; }
+                menu my-menu
+{ item ( _ ( "Label" ) , "action-name" , "icon-name" ) item { action : "win.format" ; } }
+
+
+
+
+
+
+

tests/formatting/out.blp

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+using Gtk 4.0;
+using Adw 1;
+
+Overlay {
+  Label label {
+    label: _('\'Hello World!\' "\n\t"');
+  }
+
+  [overlay]
+  Button {
+    notify::icon-name => $on_icon_name_changed (label) swapped;
+
+    styles ['destructive']
+  }
+
+  visible: bind $isVisible (label.visible, my-menu) as <bool>;
+  width-request: bind label.width-request no-sync-create;
+}
+
+menu my-menu {
+  item (_('Label'), 'action-name', 'icon-name')
+
+  item {
+    action: 'win.format';
+  }
+}

tests/test_formatter.py

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+# test_formatter.py
+#
+# Copyright 2021 James Westman <james@jwestman.net>
+#
+# This file is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# This file is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
+
+import difflib
+import unittest
+from pathlib import Path
+
+from blueprintcompiler.formatter import Format
+
+
+class TestFormatter(unittest.TestCase):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.maxDiff = None
+
+    def assert_format_test(self, input_file, expected_file):
+        print("assert_format_test({}, {})".format(input_file, expected_file))
+        with open((Path(__file__).parent / f"formatting/{input_file}").resolve()) as f:
+            input_data = f.read()
+        with open(
+            (Path(__file__).parent / f"formatting/{expected_file}").resolve()
+        ) as f:
+            expected = f.read()
+
+        actual = Format.format(input_data)
+        self.assertEqual(actual, expected)
+
+    def test_formatter(self):
+        self.assert_format_test("in1.blp", "out.blp")
+        self.assert_format_test("in2.blp", "out.blp")